1. Field of the Invention
The present invention relates to an elevator system, and in particular to a velocity instruction generation apparatus for a car of an elevator system and a velocity control method which are capable of decreasing an arithmetic operation time, operation amount and operation error and controlling the velocity of a car in real time by integer-operating a velocity instruction for controlling the velocity of the car.
2. Description of the Conventional Art
Generally, in an elevator system, a Direct Current (DC) motor or an induced motor moves an elevator car connected with the rotation axis of the motor through a cable or a pneumatic mechanism. The driving operation of the motor should be properly controlled so that an elevator car is accurately stopped and started from a certain floor of a building. In order to properly control the driving operation of the motor, variables related to the driving operation of the motor should be properly defined, and the units of the variables should be defined. The variables and the units of the variables are defined in the specification of an elevator system. Generally, the specification of the elevator system is defined in the MKS unit.
The operation controller formed of a microcomputer chip generates a velocity instruction signal of the MKS system in real time without changing the units of the constants based on the constants of the system specification of the MKS system and controls the operation of the car for thereby preventing a certain error during the operation of the elevator system, so that a certain elevator car operation is implemented.
The elevator car velocity instruction generation apparatus for a conventional elevator system will be explained.
FIG. 1 is a view illustrating a schematic block diagram of the conventional elevator system which includes an elevator car 180 for boarding passengers thereon, a door zone plate 170 installed at each floor for indicating an absolute floor, a balance weight 160 connected with the car 180 by a rope through a sheave of a winding machine (not shown), a motor 150 for upwardly and downwardly moving the car 180, a rotary encoder 140 for outputting pulses as rotating the shaft of the motor 150, a velocity controller 120 for outputting a velocity control signal for controlling the driving operation of the motor 150 in real time in accordance with the position of the car 180, an amplifier 130 for supplying an electric power to the motor 150 in accordance with the velocity control signal, a position detector 190 installed at the upper portion of the car 180 for detecting an absolute floor by detecting the door zone plate 170, and an operation controller 110 for receiving an output signal from the position detector 190 and pulses outputted from the rotary encoder 140, computing the velocity instruction signal for controlling the velocity of the car 180 and outputting to the velocity controller 120.
FIG. 2 is a view illustrating a conventional velocity instruction generation apparatus which includes a signal processing unit 111 for controlling an elevator system and computing a running distance of a car 180, an EEPROM 112 for storing the specification of the elevator system, a ROM 113 for storing a program for controlling the elevator system, a RAM 114 for temporarily storing a computation data when computing the velocity instruction signal, and a counter 115 for counting pulses.
In detail, the signal processing unit 111 includes a pulse input unit 11 for receiving a pulse signal outputted from the rotary encoder 140, a traveling distance computation unit 12 for counting the number of pulses received into the pulse input unit 11 and computing the traveling distance of the car 180, a floor height computation unit 13 for judging the present position of the car 180 based on the distance computed by the traveling distance computation unit 12, a car stop determination computation unit 14 for determining the stop position of the car 180, a time based velocity instruction computation unit 15 for transferring a velocity instruction signal corresponding to time stored in the EEPROM 112 at the time of the operation start point of the car 180 to the velocity controller 120, and a distance based velocity instruction computation unit 16 for transferring a velocity instruction signal corresponding to the distance stored in the EEPROM 112 to the velocity controller 120 with respect to the stop instruction of the car 180.
The operation of the velocity instruction generation apparatus for a conventional elevator system will be explained.
When a passenger calls the car 180 at a certain floor, the signal processing unit 111 of the operation controller 110 performs an operation control program stored in the ROM 113 and transfers the velocity instruction signal V(t) to the velocity controller 120. The velocity controller 120 which received the velocity instruction signal v(t) outputs a velocity control signal to the amplifier 130, and the amplifier 130 controls the rotation speed of the motor 150 based on the velocity control signal.
When the car 180 begins to move, the rotary encoder 140 connected with the shaft of the motor 150 outputs pulses. The running distance computation unit 12 receives the pulses via the pulse input unit 11 and computes the running distance of the car 180 by counting the number of pulses. The floor computation unit 13 computes the current floor and the previous floor of the moving or moved the car 180 based on the computed running distance of the running distance computation unit 12.
The stop determination computation unit 14 which receives the value corresponding to the current position of the car and the value corresponding to the previous floor outputted from the floor computation unit 13 computes the control values stored in the EEPROM 117 and the thusly received values and determines the destination floor at which the car 180 arrives.
When the car 180 moves to approximately the destination floor, the position detector 190 installed on the upper portion of the car 180 detects the door zone plate 170. When the position detector 190 accurately detects the position of the door zone plate 170, a certain output signal is outputted to the signal processing unit 111. Therefore, the time based velocity instruction computation unit 15 of the signal processing unit 111 is inactivated, and the distance based velocity instruction computation unit 16 is activated, so that the car 180 is stopped. The distance based velocity instruction computation unit 15 reads the distance based velocity instruction signal v(t) stored in the EEPROM 112 and outputs the velocity instruction signal v(t) to the velocity controller 120, and the velocity controller 120 outputs a velocity control signal, so that the rotation of the motor 150 is decreased and the car 180 arrives at the destination floor. When the car 180 arrives at the destination floor, the rotation of the motor 150 is stopped.
With an elevator system specification, the elevator car velocity instruction generation aparatus in accordance with the conventional art will be explained as follows.
In the specification of an elevator system, for example, if the maximum jerk Jmax is defined as 1 m/s.sup.3, the maximum acceleration Amax is defined as 1 m/s.sup.2, the maximum velocity Vmax is defined as 2 m/s, and the minimum height of a floor is defined as 2.5 m, the operation of the elevator car velocity instruction generation aparatus in accordance with the conventional art will be explained.
The velocity controller 120 controls the rotation of the motor in three types as shown in FIGS. 3 through 5 in accordance with the running distance of the car.
FIG. 3 illustrates the profiles of a velocity of a car, an acceleration and a jerk when a car runs long distance over the time, and the car decelerates at a certain time after the car reached the maximum velocity and maximum acceleration.
FIG. 4 illustrates the profiles of a velocity, an acceleration and a jerk of a car when the car runs long distance over the time, and the car does not reach the maximum velocity but reaches the maximum acceleration and then is decelerates and is stopped.
FIG. 5 illustrates the profiles of a velocity, an acceleration and a jerk of a car when the car runs short distance over the time, and the car does not reach the maximum velocity and maximum acceleration but decelerates at a certain time and then is stopped.
Here, the numeral references 31a, 32a and 33a represent velocity profiles of the car, 31b, 32b and 33b represent acceleration profiles of the car, 31c, 32c and 33c represent jerk profiles of the car, and T1 through T6 and TE represent the time points at which the movement state of the car is changed.
The velocity control method of the car for a conventional elevator system will be explained with reference to FIG. 6.
When a passenger calls a car, the operation controller detects the floor (destination floor) at which the passenger called the car and the floor (current floor) at which the car is currently positioned and computes the distance of the MKS system by computing the difference between the destination floor and the current floor.
First, the difference value between the encoder value FLH of the destination floor and the encoder value C of the current floor of the car is obtained for thereby computing the running distance L of the car in Step SP41 based on the following equation 1. EQU L'=FLH-C[pulse] (1)
At this time, the number of pulses per the unit running distance of the car 180 is computed based on the following equation (2) using the gear ratio G, the diameter D of a traction machine TM, and the number E of the encoder pulses outputted when a pulley of the motor is rotated one time. ##EQU1##
Therefore, in order to change the running distance of the car into the MKS system, the physical amount of the MKS system should be changed based on equations (1) and (2). Therefore, it is possible to obtain the running distance L[m] of the MKS system by dividing equation (1) by equation (2). ##EQU2##
Here, the jerk acceleration time Tr and minimum running distance (Lmin) of the elevator system are obtained based on equations (4) and (5). ##EQU3##
where Amax represents the maximum acceleration, and J represents a jerk.
The operation controller 110 computes a running distance L' of the pulse unit and a running distance L of the MKS units, and compares the running distance L of the car and the minimum running distance Lmin obtained based on equation 4 in Step SP 42. As a result of the comparison, if it is judged that the running distance L is smaller than the minimum running distance Lmin, since the car runs short distance, the velocity profile of the car is determined as shown in FIG. 5 in Step SP 44. If the running distance L is larger than the minimum running distance Lmin, the running distance L is compared with the running distance based on the following equation 5 in Step SP 43. ##EQU4##
At this time, if the running distance L in the Step SP 43 is larger than the running distance of equation (6), since the car runs long distance, the velocity profile of the car is determined as shown in FIG. 3 in Step SP 45. If the above-described running distance is smaller than the running distance of equation (6), since the car runs intermediate distance, the velocity profile of the car is determined as shown in FIG. 4 in Step SP 46.
When the velocity profiles of the car are determined, the operation controller 110 sets the initial time to 0 in order to determine the operation time of the car in Step SP 47 and computes the velocity instruction signal v(t) at a certain time (t) and outputs the velocity instruction v(t) to the velocity controller 120 in Step SP 48. Thereafter, the velocity controller computes the velocity control signal by the unit of the pulses in accordance with the velocity instruction signal, and the thusly computed signals are outputted to the motor 150, so that the motor 150 is controlled.
When the car 180 is moved, the rotary encoder 140 outputs the pulses, and the signal processing unit 111 receives the output pulse and computes the previous position and the current position of the car based on equation (1) in Step SP 49. In addition, the car runs depending on the set velocity profiles until the car arrives at the destination floor. Thereafter, the car computes the decelerating distance R of the car at a certain position in Step SP 50. When the car arrives at the above-described position, it is judged whether the operation time of the car 180 is decreased in Step SP 51. If the car is not decelerated, the operation velocity and position of the car 180 are computed, and the thusly computed velocity instruction signal is outputted to the velocity controller 120 in Steps SP 52, SP 48, SP 49.
When the car 180 arrives at a certain position, and the velocity of the car 180 is decreased in Step SP 50, the deceleration instruction signal v(t) of the car 180 is outputted to the velocity controller 120, and the velocity controller 120 computes the deceleration instruction signal V(t) by the unit of the encoder pulses and outputs the velocity control signal of the unit of the encoder pulse to the velocity controller 120 for thereby decreasing the rotation of the motor in Step SP 53. The operation controller 120 outputs a certain time deceleration instruction signal V(t) to the velocity controller 120 until the car 180 arrives at a certain stop position in Steps SP 54 and SP 55. If it is judged that the car 180 arrived at a certain position, the car is stopped.
In the above-described velocity instruction generation apparatus for a car of a conventional elevator system and a velocity control method thereof, in order to control the operation of the car, the variables of the unit of the encoder pulses are detected and changed to the MKS units of the specification of the elevator system for thereby computing the running distance, velocity and time of the MKS units. Next, a control signal is generated for controlling the car using the parameter of the MKS system, and the motor is controlled by changing the control signal into the units of the encoder pulses. Therefore, all computations are performed based on real number computation. In order to compute the running distance, the pulses are sampled, and the parameter of the pulse units are changed into the parameter of the MKS units based on integer computation. Therefore, the computation velocity for controlling the operation velocity of the car is decreased, and the number of the computations is increased.
In order to overcome the above-described problems, a co-processor capable of performing a real number computation is additionally required. In this case, the co-processor is expensive, and an operation speed is slow compared to the integer number computation.
In addition, in the velocity instruction generation apparatus for the car of a conventional elevator system, the specification is stored in the ROM depending on the conditions such as the number of passengers, velocity, transaction machine (T/M), etc. irrespective of the time and distance bases when computing the velocity instruction signal. Therefore, in the conventional art, in order to meet various specification conditions of the elevator system with respect to the number of passenger, the velocity of a winding machine and a motor, etc., a large capacity of ROM is required or a certain operation method which is capable of controlling various operation programs in accordance with the velocity and winding machine is used. In addition, in order to increase a resolution of the velocity instruction signal, various data should be used. Therefore, for the above-described reasons, a large number of ROM are required.
In addition, in the conventional velocity instruction generation apparatus for a car of an elevator system, since the size of the ROM is small to store the data, it is impossible to implement an accurate resolution of the previously computed velocity instruction signal. So, there is a problem that it is impossible to accurately compute the velocity instruction even when performing a distance based computation. In order to overcome the above-described problem, a plurality of ROMs capable of storing a large size of data using a certain program may be provided. In this case, the fabrication cost of the system is increased.